efi_loader: address coverity report 492766 for dead code

The check of the return code is already done a few lines above.
Although it doesn't cause any functional issues, remove the superfluous
checks

Addresses-Coverity-ID: 492766 Control flow issues  (DEADCODE)
Signed-off-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
Reviewed-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>